[JFFS2] Speed up mount for directly-mapped NOR flash

Remove excessive scanning of empty flash after a clean
marker for users of the point/unpoint method. cfi_cmdset_0001
uses point/unpoint by default iff flash mapping is linear.
The speedup is several orders of magnitude if FS is less than
half full.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index a5103df..7a46a43 100644 (file)
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -636,16 +636,17 @@ scan_more:
 
                if (*(uint32_t *)(&buf[ofs-buf_ofs]) == 0xffffffff) {
                        uint32_t inbuf_ofs;
-                       uint32_t empty_start;
+                       uint32_t empty_start, scan_end;
 
                        empty_start = ofs;
                        ofs += 4;
+                       scan_end = min_t(uint32_t, EMPTY_SCAN_SIZE(c->sector_size)/8, buf_len);
 
                        D1(printk(KERN_DEBUG "Found empty flash at 0x%08x\n", ofs));
                more_empty:
                        inbuf_ofs = ofs - buf_ofs;
-                       while (inbuf_ofs < buf_len) {
-                               if (*(uint32_t *)(&buf[inbuf_ofs]) != 0xffffffff) {
+                       while (inbuf_ofs < scan_end) {
+                               if (unlikely(*(uint32_t *)(&buf[inbuf_ofs]) != 0xffffffff)) {
                                        printk(KERN_WARNING "Empty flash at 0x%08x ends at 0x%08x\n",
                                               empty_start, ofs);
                                        if ((err = jffs2_scan_dirty_space(c, jeb, ofs-empty_start)))
@@ -666,7 +667,11 @@ scan_more:
                                D1(printk(KERN_DEBUG "%d bytes at start of block seems clean... assuming all clean\n", EMPTY_SCAN_SIZE(c->sector_size)));
                                return BLK_STATE_CLEANMARKER;
                        }
-
+                       if (!buf_size && (scan_end != buf_len)) {/* XIP/point case */
+                               scan_end = buf_len;
+                               goto more_empty;
+                       }
+                       
                        /* See how much more there is to read in this eraseblock... */
                        buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
                        if (!buf_len) {
@@ -676,6 +681,8 @@ scan_more:
                                          empty_start));
                                break;
                        }
+                       /* point never reaches here */
+                       scan_end = buf_len;
                        D1(printk(KERN_DEBUG "Reading another 0x%x at 0x%08x\n", buf_len, ofs));
                        err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
                        if (err)